/* Functionality for finding, storing, and restoring selections
 *
 * This does not provide a generic API, just the minimal functionality
 * required by the CodeMirror system.
 */

// Namespace object.
var select = {};

(function() {
  select.ie_selection = document.selection && document.selection.createRangeCollection;

  // Find the 'top-level' (defined as 'a direct child of the node
  // passed as the top argument') node that the given node is
  // contained in. Return null if the given node is not inside the top
  // node.
  function topLevelNodeAt(node, top) {
	while (node && node.parentNode != top)
	  node = node.parentNode;
	return node;
  }

  // Find the top-level node that contains the node before this one.
  function topLevelNodeBefore(node, top) {
	while (!node.previousSibling && node.parentNode != top)
	  node = node.parentNode;
	return topLevelNodeAt(node.previousSibling, top);
  }

  // Used to prevent restoring a selection when we do not need to.
  var currentSelection = null;

  var fourSpaces = "\u00a0\u00a0\u00a0\u00a0";

  select.snapshotChanged = function() {
	if (currentSelection) currentSelection.changed = true;
  };

  // This is called by the code in editor.js whenever it is replacing
  // a text node. The function sees whether the given oldNode is part
  // of the current selection, and updates this selection if it is.
  // Because nodes are often only partially replaced, the length of
  // the part that gets replaced has to be taken into account -- the
  // selection might stay in the oldNode if the newNode is smaller
  // than the selection's offset. The offset argument is needed in
  // case the selection does move to the new object, and the given
  // length is not the whole length of the new node (part of it might
  // have been used to replace another node).
  select.snapshotReplaceNode = function(from, to, length, offset) {
	if (!currentSelection) return;
	currentSelection.changed = true;

	function replace(point) {
	  if (from == point.node) {
		if (length && point.offset > length) {
		  point.offset -= length;
		}
		else {
		  point.node = to;
		  point.offset += (offset || 0);
		}
	  }
	}
	replace(currentSelection.start);
	replace(currentSelection.end);
  };

  select.snapshotMove = function(from, to, distance, relative, ifAtStart) {
	if (!currentSelection) return;
	currentSelection.changed = true;

	function move(point) {
	  if (from == point.node && (!ifAtStart || point.offset == 0)) {
		point.node = to;
		if (relative) point.offset = Math.max(0, point.offset + distance);
		else point.offset = distance;
	  }
	}
	move(currentSelection.start);
	move(currentSelection.end);
  };

  // Most functions are defined in two ways, one for the IE selection
  // model, one for the W3C one.
  if (select.ie_selection) {
	function selectionNode(win, start) {
	  var range = win.document.selection.createRange();
	  range.collapse(start);

	  function nodeAfter(node) {
		var found = null;
		while (!found && node) {
		  found = node.nextSibling;
		  node = node.parentNode;
		}
		return nodeAtStartOf(found);
	  }

	  function nodeAtStartOf(node) {
		while (node && node.firstChild) node = node.firstChild;
		return {node: node, offset: 0};
	  }

	  var containing = range.parentElement();
	  if (!isAncestor(win.document.body, containing)) return null;
	  if (!containing.firstChild) return nodeAtStartOf(containing);

	  var working = range.duplicate();
	  working.moveToElementText(containing);
	  working.collapse(true);
	  for (var cur = containing.firstChild; cur; cur = cur.nextSibling) {
		if (cur.nodeType == 3) {
		  var size = cur.nodeValue.length;
		  working.move("character", size);
		}
		else {
		  working.moveToElementText(cur);
		  working.collapse(false);
		}

		var dir = range.compareEndPoints("StartToStart", working);
		if (dir == 0) return nodeAfter(cur);
		if (dir == 1) continue;
		if (cur.nodeType != 3) return nodeAtStartOf(cur);

		working.setEndPoint("StartToEnd", range);
		return {node: cur, offset: size - working.text.length};
	  }
	  return nodeAfter(containing);
	}

	select.markSelection = function(win) {
	  currentSelection = null;
	  var sel = win.document.selection;
	  if (!sel) return;
	  var start = selectionNode(win, true),
		  end = sel.createRange().text == "" ? start : selectionNode(win, false);
	  if (!start || !end) return;
	  currentSelection = {start: start, end: end, window: win, changed: false};
	};

	select.selectMarked = function() {
	  if (!currentSelection || !currentSelection.changed) return;

	  function makeRange(point) {
		var range = currentSelection.window.document.body.createTextRange();
		var node = point.node;
		if (!node) {
		  range.moveToElementText(currentSelection.window.document.body);
		  range.collapse(false);
		}
		else if (node.nodeType == 3) {
		  range.moveToElementText(node.parentNode);
		  var offset = point.offset;
		  while (node.previousSibling) {
			node = node.previousSibling;
			offset += (node.innerText || "").length;
		  }
		  range.move("character", offset);
		}
		else {
		  range.moveToElementText(node);
		  range.collapse(true);
		}
		return range;
	  }

	  var start = makeRange(currentSelection.start), end = makeRange(currentSelection.end);
	  start.setEndPoint("StartToEnd", end);
	  start.select();
	};

	// Get the top-level node that one end of the cursor is inside or
	// after. Note that this returns false for 'no cursor', and null
	// for 'start of document'.
	select.selectionTopNode = function(container, start) {
	  var selection = container.ownerDocument.selection;
	  if (!selection) return false;

	  var range = selection.createRange();
	  range.collapse(start);
	  var around = range.parentElement();
	  if (around && isAncestor(container, around)) {
		// Only use this node if the selection is not at its start.
		var range2 = range.duplicate();
		range2.moveToElementText(around);
		if (range.compareEndPoints("StartToStart", range2) == -1)
		  return topLevelNodeAt(around, container);
	  }
	  // Fall-back hack
	  try {range.pasteHTML("<span id='xxx-temp-xxx'></span>");}
	  catch (e) {return false;}

	  var temp = container.ownerDocument.getElementById("xxx-temp-xxx");
	  if (temp) {
		var result = topLevelNodeBefore(temp, container);
		removeElement(temp);
		return result;
	  }
	  return false;
	};

	// Place the cursor after this.start. This is only useful when
	// manually moving the cursor instead of restoring it to its old
	// position.
	select.focusAfterNode = function(node, container) {
	  var range = container.ownerDocument.body.createTextRange();
	  range.moveToElementText(node || container);
	  range.collapse(!node);
	  range.select();
	};

	select.somethingSelected = function(win) {
	  var sel = win.document.selection;
	  return sel && (sel.createRange().text != "");
	};

	function insertAtCursor(window, html) {
	  var selection = window.document.selection;
	  if (selection) {
		var range = selection.createRange();
		range.pasteHTML(html);
		range.collapse(false);
		range.select();
	  }
	}

	// Used to normalize the effect of the enter key, since browsers
	// do widely different things when pressing enter in designMode.
	select.insertNewlineAtCursor = function(window) {
	  insertAtCursor(window, "<br>");
	};

	select.insertTabAtCursor = function(window) {
	  insertAtCursor(window, fourSpaces);
	};

	// Get the BR node at the start of the line on which the cursor
	// currently is, and the offset into the line. Returns null as
	// node if cursor is on first line.
	select.cursorPos = function(container, start) {
	  var selection = container.ownerDocument.selection;
	  if (!selection) return null;

	  var topNode = select.selectionTopNode(container, start);
	  while (topNode && topNode.nodeName != "BR")
		topNode = topNode.previousSibling;

	  var range = selection.createRange(), range2 = range.duplicate();
	  range.collapse(start);
	  if (topNode) {
		range2.moveToElementText(topNode);
		range2.collapse(false);
	  }
	  else {
		// When nothing is selected, we can get all kinds of funky errors here.
		try { range2.moveToElementText(container); }
		catch (e) { return null; }
		range2.collapse(true);
	  }
	  range.setEndPoint("StartToStart", range2);

	  return {node: topNode, offset: range.text.length};
	};

	select.setCursorPos = function(container, from, to) {
	  function rangeAt(pos) {
		var range = container.ownerDocument.body.createTextRange();
		if (!pos.node) {
		  range.moveToElementText(container);
		  range.collapse(true);
		}
		else {
		  range.moveToElementText(pos.node);
		  range.collapse(false);
		}
		range.move("character", pos.offset);
		return range;
	  }

	  var range = rangeAt(from);
	  if (to && to != from)
		range.setEndPoint("EndToEnd", rangeAt(to));
	  range.select();
	}

	// Make sure the cursor is visible.
	select.scrollToCursor = function(container) {
	  var selection = container.ownerDocument.selection;
	  if (!selection) return null;
	  selection.createRange().scrollIntoView();
	};

	select.scrollToNode = function(node) {
	  if (!node) return;
	  node.scrollIntoView();
	};

	// Some hacks for storing and re-storing the selection when the editor loses and regains focus.
	select.selectionCoords = function (win) {
	  var selection = win.document.selection;
	  if (!selection) return null;
	  var start = selection.createRange(), end = start.duplicate();
	  start.collapse(true);
	  end.collapse(false);

	  var body = win.document.body;
	  return {start: {x: start.boundingLeft + body.scrollLeft - 1,
					  y: start.boundingTop + body.scrollTop},
			  end: {x: end.boundingLeft + body.scrollLeft - 1,
					y: end.boundingTop + body.scrollTop}};
	};

	// Restore a stored selection.
	select.selectCoords = function(win, coords) {
	  if (!coords) return;

	  var range1 = win.document.body.createTextRange(), range2 = range1.duplicate();
	  // This can fail for various hard-to-handle reasons.
	  try {
		range1.moveToPoint(coords.start.x, coords.start.y);
		range2.moveToPoint(coords.end.x, coords.end.y);
		range1.setEndPoint("EndToStart", range2);
		range1.select();
	  } catch(e) {alert(e.message);}
	};
  }
  // W3C model
  else {
	// Store start and end nodes, and offsets within these, and refer
	// back to the selection object from those nodes, so that this
	// object can be updated when the nodes are replaced before the
	// selection is restored.
	select.markSelection = function (win) {
	  var selection = win.getSelection();
	  if (!selection || selection.rangeCount == 0)
		return (currentSelection = null);
	  var range = selection.getRangeAt(0);

	  currentSelection = {
		start: {node: range.startContainer, offset: range.startOffset},
		end: {node: range.endContainer, offset: range.endOffset},
		window: win,
		changed: false
	  };

	  // We want the nodes right at the cursor, not one of their
	  // ancestors with a suitable offset. This goes down the DOM tree
	  // until a 'leaf' is reached (or is it *up* the DOM tree?).
	  function normalize(point){
		while (point.node.nodeType != 3 && point.node.nodeName != "BR") {
		  var newNode = point.node.childNodes[point.offset] || point.node.nextSibling;
		  point.offset = 0;
		  while (!newNode && point.node.parentNode) {
			point.node = point.node.parentNode;
			newNode = point.node.nextSibling;
		  }
		  point.node = newNode;
		  if (!newNode)
			break;
		}
	  }

	  normalize(currentSelection.start);
	  normalize(currentSelection.end);
	};

	select.selectMarked = function () {
	  if (!currentSelection || !currentSelection.changed) return;
	  var win = currentSelection.window, range = win.document.createRange();

	  function setPoint(point, which) {
		if (point.node) {
		  // Some magic to generalize the setting of the start and end
		  // of a range.
		  if (point.offset == 0)
			range["set" + which + "Before"](point.node);
		  else
			range["set" + which](point.node, point.offset);
		}
		else {
		  range.setStartAfter(win.document.body.lastChild || win.document.body);
		}
	  }

	  setPoint(currentSelection.end, "End");
	  setPoint(currentSelection.start, "Start");
	  selectRange(range, win);
	};

	// Helper for selecting a range object.
	function selectRange(range, window) {
	  var selection = window.getSelection();
	  selection.removeAllRanges();
	  selection.addRange(range);
	};
	function selectionRange(window) {
	  var selection = window.getSelection();
	  if (!selection || selection.rangeCount == 0)
		return false;
	  else
		return selection.getRangeAt(0);
	}

	// Finding the top-level node at the cursor in the W3C is, as you
	// can see, quite an involved process.
	select.selectionTopNode = function(container, start) {
	  var range = selectionRange(container.ownerDocument.defaultView);
	  if (!range) return false;

	  var node = start ? range.startContainer : range.endContainer;
	  var offset = start ? range.startOffset : range.endOffset;
	  // Work around (yet another) bug in Opera's selection model.
	  if (window.opera && !start && range.endContainer == container && range.endOffset == range.startOffset + 1 &&
		  container.childNodes[range.startOffset] && container.childNodes[range.startOffset].nodeName == "BR")
		offset--;

	  // For text nodes, we look at the node itself if the cursor is
	  // inside, or at the node before it if the cursor is at the
	  // start.
	  if (node.nodeType == 3){
		if (offset > 0)
		  return topLevelNodeAt(node, container);
		else
		  return topLevelNodeBefore(node, container);
	  }
	  // Occasionally, browsers will return the HTML node as
	  // selection. If the offset is 0, we take the start of the frame
	  // ('after null'), otherwise, we take the last node.
	  else if (node.nodeName == "HTML") {
		return (offset == 1 ? null : container.lastChild);
	  }
	  // If the given node is our 'container', we just look up the
	  // correct node by using the offset.
	  else if (node == container) {
		return (offset == 0) ? null : node.childNodes[offset - 1];
	  }
	  // In any other case, we have a regular node. If the cursor is
	  // at the end of the node, we use the node itself, if it is at
	  // the start, we use the node before it, and in any other
	  // case, we look up the child before the cursor and use that.
	  else {
		if (offset == node.childNodes.length)
		  return topLevelNodeAt(node, container);
		else if (offset == 0)
		  return topLevelNodeBefore(node, container);
		else
		  return topLevelNodeAt(node.childNodes[offset - 1], container);
	  }
	};

	select.focusAfterNode = function(node, container) {
	  var win = container.ownerDocument.defaultView,
		  range = win.document.createRange();
	  range.setStartBefore(container.firstChild || container);
	  // In Opera, setting the end of a range at the end of a line
	  // (before a BR) will cause the cursor to appear on the next
	  // line, so we set the end inside of the start node when
	  // possible.
	  if (node && !node.firstChild)
		range.setEndAfter(node);
	  else if (node)
		range.setEnd(node, node.childNodes.length);
	  else
		range.setEndBefore(container.firstChild || container);
	  range.collapse(false);
	  selectRange(range, win);
	};

	select.somethingSelected = function(win) {
	  var range = selectionRange(win);
	  return range && !range.collapsed;
	};

	function insertNodeAtCursor(window, node) {
	  var range = selectionRange(window);
	  if (!range) return;

	  range.deleteContents();
	  range.insertNode(node);
	  webkitLastLineHack(window.document.body);
	  range = window.document.createRange();
	  range.selectNode(node);
	  range.collapse(false);
	  selectRange(range, window);
	}

	select.insertNewlineAtCursor = function(window) {
	  insertNodeAtCursor(window, window.document.createElement("BR"));
	};

	select.insertTabAtCursor = function(window) {
	  insertNodeAtCursor(window, window.document.createTextNode(fourSpaces));
	};

	select.cursorPos = function(container, start) {
	  var range = selectionRange(window);
	  if (!range) return;

	  var topNode = select.selectionTopNode(container, start);
	  while (topNode && topNode.nodeName != "BR")
		topNode = topNode.previousSibling;

	  range = range.cloneRange();
	  range.collapse(start);
	  if (topNode)
		range.setStartAfter(topNode);
	  else
		range.setStartBefore(container);
	  return {node: topNode, offset: range.toString().length};
	};

	select.setCursorPos = function(container, from, to) {
	  var win = container.ownerDocument.defaultView,
		  range = win.document.createRange();

	  function setPoint(node, offset, side) {
		if (!node)
		  node = container.firstChild;
		else
		  node = node.nextSibling;

		if (!node)
		  return;

		if (offset == 0) {
		  range["set" + side + "Before"](node);
		  return true;
		}

		var backlog = []
		function decompose(node) {
		  if (node.nodeType == 3)
			backlog.push(node);
		  else
			forEach(node.childNodes, decompose);
		}
		while (true) {
		  while (node && !backlog.length) {
			decompose(node);
			node = node.nextSibling;
		  }
		  var cur = backlog.shift();
		  if (!cur) return false;

		  var length = cur.nodeValue.length;
		  if (length >= offset) {
			range["set" + side](cur, offset);
			return true;
		  }
		  offset -= length;
		}
	  }

	  to = to || from;
	  if (setPoint(to.node, to.offset, "End") && setPoint(from.node, from.offset, "Start"))
		selectRange(range, win);
	};

	select.scrollToNode = function(element) {
	  if (!element) return;
	  var doc = element.ownerDocument, body = doc.body, win = doc.defaultView, html = doc.documentElement;

	  // In Opera, BR elements *always* have a scrollTop property of zero. Go Opera.
	  while (element && !element.offsetTop)
		element = element.previousSibling;

	  var y = 0, pos = element;
	  while (pos && pos.offsetParent) {
		y += pos.offsetTop;
		pos = pos.offsetParent;
	  }

	  var screen_y = y - (body.scrollTop || html.scrollTop || 0);
	  if (screen_y < 0 || screen_y > win.innerHeight - 30)
		win.scrollTo(body.scrollLeft || html.scrollLeft || 0, y);
	};

	select.scrollToCursor = function(container) {
	  select.scrollToNode(select.selectionTopNode(container, true) || container.firstChild);
	};
  }
})();
